Previously call-with-transaction would both retry when SQLITE_BUSY errors were
thrown and do what its name suggested (start and rollback/commit a
transaction). This changes it to do only what its name implies, which
simplifies its implementation. Retrying is provided by the new
call-with-SQLITE_BUSY-retrying procedure.
* guix/store/database.scm (call-with-transaction): no longer restarts, new
#:restartable? argument controls whether "begin" or "begin immediate" is
used.
(call-with-SQLITE_BUSY-retrying, call-with-retrying-transaction,
call-with-retrying-savepoint): new procedures.
(register-items): use call-with-retrying-transaction to preserve old
behavior.
* .dir-locals.el (call-with-retrying-transaction,
call-with-retrying-savepoint): add indentation information.